Method for treating suspended solids

ABSTRACT

Water-soluble, branched, high molecular weight, cationic and non-ionic polymeric flocculants capable of manifesting their full performance potential without shearing are produced by polymerizing ethylenically unsaturated cationic and non-ionic monomers and a branching agent in the presence of a chain-transfer agent. They are useful as flocculating agents for releasing water from dispersions of suspended solids.

This is a continuation of U.S. application Ser. No. 08/028,001, filedMar. 8, 1993 and now abandoned, which in turn is a continuation of U.S.application Ser. No. 07/551,228, filed Jul. 9, 1990 and now abandoned,which in turn is a divisional of U.S. application Ser. No. 07/285,953,filed Dec. 19, 1988 and now abandoned.

The present invention relates to unsheared, high molecular weight,highly branched, water-soluble, polymers and, more particularly, to amethod of preparing such polymer compositions, and their use asflocculating agents.

BACKGROUND OF THE INVENTION

Flocculation is a form of liquid-solid phase separation whichfacilitates the removal of finely divided particles from a liquid byenhancing agglomeration of suspended particles in order to increaseparticle size, and is often applied to enable conformity with effluentclarity requirements. Flocculation may be accomplished by chemicalmeans, e.g., addition of a flocculating agent.

Synthetic, organic, polymeric, flocculating agents have been utilized inindustry since the 1950's. It has been observed, by those skilled in theart, that high molecular weight polymers are particularly useful aschemical flocculating agents, provided that the polymers arewater-soluble. Many such water-soluble, high molecular weight,polymeric, flocculating agents are known to those skilled in this art.

Linear, water-soluble polymers have been used as flocculating agents inthe treatment of waste sludges with some degree of success. However, dueto modern concerns with environmental protection, sludge incinerationand transportation costs, it has become increasingly desirable toimprove on the performance of conventional, linear flocculants byproviding a flocculating agent which causes the formation of higher cakesolids.

The present invention provides a method for preparing a novel, highlybranched, high molecular weight water-soluble, polymeric flocculantusing a polyfunctional monomer such as methylenebisacrylamide,polyethyleneglycol dimethacrylate, n-vinyl acrylamide and the like, as abranching agent. The prior art discloses several attempts to producehigh molecular weight, branched, water-soluble polymers. Zweigle, U.S.Pat. No. 4,059,522 discloses the use of branching agents to yield atotally crosslinked system, but flocculants prepared in this manner areinsoluble in water and thus ineffective. Morgan, et al., U.S. Pat. No.3,698,037 discloses branched, cationic homopolymers obtained throughincorporation of a multifunctional branching agent in the absence of amolecular weight controlling or chain-transfer agent. It is well knownto those skilled in the art, that the molecular weight of such cationichomopolymers is limited, whereas much higher molecular weight polymersmay be obtained by copolymerizing cationic monomers with acrylamides.The above discussed patent makes no mention of molecular weightspecifics.

Pech, Fr. 2,589,145 discloses a branched copolymer prepared usingsolution polymerization techniques in the presence of a high activitychain-transfer agent. However, the polymers disclosed in this patenthave molecular weights below 1 million with solution viscosities of 2200to 3600 mPa•s at 20 percent polymer concentrations, thus showing thesepolymers to be truly low molecular weight copolymers. The lowestmolecular weight polymer of the present invention is much higher,greater than 1 million, and has a solution viscosity of 5,570 mPa•s atonly 2.32 percent polymer concentration. (See Example 36C).

Other patent disclosures use shearing of crosslinked polymer chains toobtain desired water-solubility. Whittaker, U.S. Pat. No. 4,705,640discloses the shearing of crosslinked polymer gels which are insolublein water to physically degrade them to such an extent that they becomewater-soluble. The preferred method of degradation is mechanical with ahigh degree of chopping type action, such as subjecting dilute solutionsof polymer to rotating blades at up to 20,000 rpm. Degradation isclaimed to improve flocculation performance by increasing the effectiveionicity of the polymer. The increase in effective ionicity isquantified by measuring the ionic regain (IR); IR=(IAD-IBD)/IAD×100where IAD is the ionicity after degradation and IBD is the ionicitybefore degradation. The ionicity can be measured by a colloid titrationtechnique as described therein and also Flesher et al, U.S. Pat. No.4,720,346, which discloses a process for flocculating aqueoussuspensions of solids by the use of a polymeric material in the form ofsmall particles rather than a true solution. Flesher et al also disclosethe need to shear crosslinked polymer materials, such that the polymerhas an ionic regain value of 15 to 70 percent, since polymers having toolow an IR value give an inadequate benefit. Flesher et al define shearas that which is applied as an analytical technique to impart propertieson polymers, such as IR, so that the polymers may be used in thatinvention. In Column 11, lines 3-10, Flesher et al further disclose thathigher flocculant dose levels are needed to achieve optimum flocstability, sometimes 20 percent more than dose requirements ofconventional, water-soluble linear polymers.

Flesher indicates that branched copolymers can be prepared by usingchain-transfer agents, such as isopropanol and mercaptoethanol, inconjunction with cross-linking agents. However, no examples areprovided, and it appears quite unlikely that Flesher discoveredcompositions corresponding to those claimed herein which outperform theFlesher materials and are simpler to use.

Farrar, in U.S. Pat. No. 4,759,856, also describes, in Column 6, lines1-6, the need to apply shear to convert crosslinked polymers that wouldnormally have been rejected or that would have been expected to havegiven poor flocculation properties to a form in which it will give verygood flocculation properties. The patentee teaches shearing in such amanner that the polymer undergoes an ionic regain of at least 15percent, preferably at least 30 percent, and usually at least 50percent, as a result of the shearing, to effect a conversion to a usefulpolymer flocculant.

Surprisingly, it has now been discovered that high molecular weight,highly branched, water-soluble, polymeric flocculants can be producedwithout the use of high level shear and independent of ionic regainvalues. Polymeric flocculants produced by the practice of the presentinvention are subjected only to minimal levels of shear, sufficient onlyto cause solubilization with little or no physical degradation of thepolymer. Furthermore, the polymeric flocculants of the present inventionencompass IR values ranging from about 0 to about 70 percent, andimproved performance of these polymers is not enhanced by increase ineffective ionicity, but instead they perform as well at ionicity levelswithin the scope of the prior art as well as without. Polymericflocculants of the present invention outperform the flocculants of theprior art, consistently producing high levels of cake solids often atlower dose levels. Additionally, polymeric flocculants of this inventionand their mixtures are more convenient and less costly to use than priorart flocculants which require the end user to employ high shearequipment prior to use, in order to gain the desired optimumflocculation effect, thus increasing both the time and cost of theoperation.

The present invention enables the preparation of truly water-soluble,highly branched, high molecular weight, polymers particularly useful aschemical flocculating agents. The polymers of this invention areprepared using a branching agent in the presence of a chain-transferagent to produce a product which is highly branched and water-soluble.Additionally, the polymers of this invention do not require theapplication of controlled shear to attain optimum performance, therebysaving additional costs. The present invention has particularly beenfound useful when applied to branched copolymers comprising acrylamideand at least one ethylenically unsaturated cationic, or non-ionicmonomer.

SUMMARY OF THE INVENTION

According to the present invention, there are provided unsheared,cationic, water-soluble, branched, polymeric flocculants, said polymericflocculants having a solution viscosity of at least 1.8 mPa•s measuredin a Brookfield viscometer with a UL adapter at 25° C. on a 0.1 percent,by weight, polymer solution in 1M NaCl at 60 rpm, a solubility quotientof greater than about 30 percent, and a branching agent content of fromabout 4 to about 80 molar parts per million based on initial monomercontent. Preferably, the polymeric flocculants possess a solubilityquotient of greater than about 40 percent, the branching agent comprisesfrom about 8 to about 20 molar parts per million based on originalmonomer content and exhibit a solution viscosity of at least about 2.4mPa•s measured in a Brookfield viscometer with a UL adapter at 25° C. ona 0.1 percent, by weight, polymer solution in 1M NaCl at 60 rpm. Forpurposes of this invention, the term "unsheared," when used herein andin the appended claims, does not exclude normal mixing which is used todisperse polymers. For example, mixing with a magnetic stirrer, as willbe described hereinafter, will not produce a "sheared" polymer but thepolymer will be "unsheared" within the meaning of the claims even after2 hours of mixing.

Also, according to the present invention there is provided a process forthe preparation of an unsheared, water-soluble, branched, polymeric,cationic flocculant, as above defined, said process comprisingpolymerizing one or more cationic, ethylenically unsaturated monomerswith at least one branching agent in an amount from about 4 to about 80molar parts per million based on initial monomer content, in thepresence of at least one chain-transfer agent in an amount at leastsufficient to provide said polymeric flocculant with a solubilityquotient of greater than about 30 percent.

Preferably, such a process calls for the addition of from about 8 toabout 20 molar parts per million, based on original monomer content, ofbranching agent, wherein the branched polymeric flocculant has asolubility quotient of greater than about 40 percent and has a solutionviscosity of at least about 2.4 mPa•s measured in a Brookfieldviscometer with a UL adapter at 25° C. on a 0.1 percent, by weight,polymer solution in 1M NaCl at 60 rpm.

According to the present invention there are also provided non-ionic,water-soluble, highly branched, polymeric flocculants comprising one ormore ethylenically unsaturated, non-ionic monomers, said polymericflocculants having a solution viscosity of at least about 1.9 mPa•s,preferably at least about 2.4 mPa•s, measured in a Brookfield viscometerwith a UL adapter at 25° C. on a 0.1 percent, by weight, polymersolution in 1M NaCl at 60 rpm, a branching agent content of from about 4to about 80 molar parts per million based on initial monomer content,and a process for the preparation of the polymeric flocculant therein.

Furthermore, according to the present invention, there are providedmethods of flocculating dispersions of suspended solids, such as sewagesludge, which comprise (a) adding to the dispersion from about 0.1 toabout 50,000 parts per million of an unsheared, water-soluble, branched,polymeric, cationic or non-ionic flocculant, as above defined above, and(b) dewatering the dispersion of suspended solids and polymericflocculant.

DETAILED DESCRIPTION OF THE INVENTION

High molecular weight, unsheared, highly branched, water-soluble,polymeric flocculants are formed by the polymerization of cationicand/or nonionic ethylenically unsaturated monomers, alone or withcomonomers, and in the presence of a branching agent and achain-transfer agent in optimum proportions.

Cationic monomers useful in the practice of this invention includediallyldimethylammonium chloride; acryloxyethyltrimethylammoniumchloride; (meth)acrylates of N,N-dialkylaminoalkyl compounds; andquaternaries and salts thereof, such as N,N-dimethylaminoethylacrylatemethylchloride salt; monomers of N,N-dialkylaminoalkyl(meth)acrylamides; and salts and quaternaries thereof, such asN,N-dialkylaminoethylacrylamides; methacrylamidopropyltrimethylammoniumchloride; 1-methacryloyl-4-methyl piperazine and the like. Cationicmonomers are generally of the following formulae; ##STR1## where R₁ ishydrogen or methyl, R₂ is hydrogen or lower alkyl of C₁ to C₄, R₃ and/orR₄ are hydrogen, alkyl of C₁ to C₁₂, aryl or hydroxyethyl and R₂ and R₃or R₂ and R4 can combine to form a cyclic ring containing one or morehetero atoms, and Z is the conjugate base of an acid, X is oxygen or--NR₁ -- wherein R₁ is as defined above, and A is an alkylene group ofC₁ to C₁₂ ; or ##STR2## where R₅ and R₆ are hydrogen or methyl, R₇ ishydrogen, alkyl of C₁ to C₁₂ or benzyl, and R₈ is hydrogen, alkyl of C₁to C₁₂ benzyl or hydroxyethyl; and Z is as defined above.

Nonionic monomers, suitable in the practice of this invention, generallycomprise acrylamide; methacrylamide; N-alkylacrylamides, such asN-methylacryl-amide; N,N-dialkylacrylamides, such asN,N-dimethylacrylamide; methyl acrylate; methyl methacrylate;acrylonitrile; N-vinylmethylacetamide or formamide; N-vinyl acetate orvinyl pyrrolidone, and the like.

These ethylenically unsaturated monomers may be copolymerized to producecationic or nonionic copolymers. Preferably, a nonionic monomer, such asan acrylamide is copolymerized with a cationic comonomer to produce acationic copolymer. Cationic copolymers useful in the practice of thisinvention, comprise from about 1 to about 99 parts, by weight, of anacrylamide monomer and from about 99 to about 1 part, by weight, of acationic comonomer. Preferably, the copolymer comprises from about 10 toabout 99 parts, by weight, of an acrylamide monomer and from about 90 toabout 1.0 part, by weight, of a cationic comonomer.

Polymerization of the monomers is conducted in the presence of apolyfunctional branching agent to form the branched homopolymer orcopolymer. The polyfunctional branching agent comprises compounds havingeither at least two double bonds, a double bond and a reactive group ortwo reactive groups. Polyfunctional branching agents should have atleast some water-solubility. Illustrative of those compounds containingat least two double bonds are methylenebisacrylamide;methylenebismethacrylamide; polyethyleneglycol diacrylate;polyethyleneglycol dimethacrylate; N-vinyl acrylamide; divinylbenzene;triallylammonium salts; N-methylallylacrylamide; and the like.Polyfunctional branching agents containing at least one double bond andat least one reactive group include glycidyl acrylate; acrolein;methylolacrylamide; and the like. Polyfunctional branching agentscontaining at least two reactive groups include aldehydes, such asglyoxal; diepoxy compounds and epichlorohydrin and the like.

Branching agents should be used in sufficient quantities to assure ahighly branched copolymer product. Preferably, a branching agent contentof from about 4 to about 80 molar parts per million, based on initialmonomer content, is added to-induce sufficient branching of the polymerchain.

Essential to the practice of this invention is the addition of, inoptimum concentration, a molecular weight modifying or chain-transferagent to control the structure and solubility of the polymer. In theabsence of a chain-transfer agent, the incorporation of even extremelysmall amounts of branching agent, e.g. 5 parts per million may causecrosslinking, rendering the polymer insoluble in water. However,soluble, highly branched, copolymer products are obtained in accordancewith the present invention when a chain-transfer agent is used, inoptimum concentration, in conjunction with said branching agent. Manysuch chain-transfer agents are well known to those skilled in the art.These include alcohols; mercaptans; thioacids; phosphites and sulfites,such as isopropyl alcohol and sodium hypophosphite, although manydifferent chain-transfer agents may be employed.

It is extremely important that optimum concentrations of chain-transferagent be employed in order to produce a highly branched, water-solubleproduct. Addition of too little chain-transfer agent produces anon-soluble copolymer product and the addition of too muchchain-transfer agent produces a product with too low a solutionviscosity, i.e. molecular weight.

The optimum concentration of chain-transfer agent, can be determined bymeasuring the solubility quotient. For purposes of this invention,solubility quotient is defined as the total mole % cationicity in thepolymer as determined by an anion binding technique (CEQ), e.g. colloidtitration, divided by the total cationicity as determined by ananalytical technique which does not depend on anion binding, using,e.g., nuclear magnetic resonance, infra red spectroscopy or chemicalanalysis, the quotient of which is multiplied by 100. The cationicity isdetermined by measuring the CEQ as described in Volume 62, Number 7 ofthe Journal of Chemical Education dated July 1985 at pages 627 to 629,which comprises measuring the cationicity of a solution using colloidtitration to determine the solubility in water. Use of a chain-transferagent in concentrations such that the solubility quotient is less than30 percent provides products that are not soluble. Only when optimumconcentrations are used, effectuating a solubility quotient greater than30 percent, do the polymers exhibit the required solubilitycharacteristics. Thus, the soluble polymers of this invention allpossess a minimum solubility quotient of over 30 percent, preferablyover 40 percent and even more preferably over 50 percent. Many exhibit asolubility quotient of greater than 90 percent.

In the case of nonionic polymers, chain-transfer agent is added in anamount sufficient to provide the polymer-with a solution viscosity of atleast about 1.9 mPa•s measured in a Brookfield viscometer with ULadapter at 25° C. on a 0.1 percent solution, by weight, polymer solutionin 1M NaCl at 60 rpm and thus achieve requisite solubility.

Actual polymerization may be carried out using gel or emulsion(suspension) polymerization techniques. These techniques are widelyknown to those skilled in the art.

Emulsion polymerization procedures involve the preparation of twophases. The aqueous phase comprises the monomer(s), branching agent andchain-transfer agent dissolved in deionized water, and other additiveswell known to those skilled in this art, such as stabilizers and pHadjusters. The oil phase comprises a water-insoluble hydrocarbonsolution of surfactant(s). The aqueous phase and oil phase are thenmixed and homogenized in a conventional apparatus until particle size isin the 1.0 micron range and a suitable bulk viscosity is obtained. Theemulsion is then transferred to a suitable flask wherein the emulsion isagitated and sparged with nitrogen for about thirty minutes. Apolymerization initiator, such as sodium metabisulfite solution, is thencontinuously added to the solution to begin polymerization.Polymerization is allowed to exotherm to the desired temperature whichis maintained by cooling until cooling is no longer required. Finishedemulsion product is cooled to 25° C.

In a typical gel polymerization procedure, monomer(s), branching agentand chain-transfer agent are dissolved in deionized water and the pH isadjusted as desired. The solution is placed in a polymerization vesseland sparged with nitrogen with the temperature of the solution beingadjusted to about 6.0° C. An initiator is then added, and thepolymerization is allowed to exotherm to maximum temperature. Oncemaximum temperature is attained, the media is placed in an oven at about70° C. for about 8 hours. The resulting gel is reduced to gel worms, airdried and reduced to powder.

Any conventional additives may be used to stabilize the aqueous phaseand oil phase solution. Suitable additives include ammonium sulfate;ethylenediaminetetraacetic acid (disodium salt) and diethylenetriaminepentaacetate (pentasodium salt). See Modern PlasticsEncyclopedia/88, McGraw Hill, October 1987, pp. 147-8.

Any known initiator may be employed to initiate polymerization. Suitablefor use in this invention are azobisisobutyronitrile; sodium sulfite;sodium metabisulfite; 2,2'-azobis(2-methyl-2-amidino-propane)dihydrochloride; ammonium persulfate and ferrous ammonium sulfatehexahydrate, and the like. organic peroxides may also be employed forpolymerizing ethylenically unsaturated monomers. Particularly useful forthe purpose of this invention is t-butyl hydroperoxide. See ModernPlastics Encyclopedia/88, McGraw Hill, October 1987, pp. 165-8.

The product so prepared is an unsheared, high molecular weight, highlybranched, water-soluble, cationic or non-ionic polymer specially suitedfor use as a chemical flocculating agent without requiring the use ofcontrolled shear to attain optimum performance.

The flocculation and dewatering stages of this invention, to releasewater from a dispersion of suspended solids, are carried out by addingthe unsheared, highly branched, high molecular weight, water-soluble,cationic or non-ionic polymeric flocculant in solution to the suspensionand then using a conventional dewatering apparatus to remove water fromthe suspension, producing a crystal clear effluent.

The products of this invention are useful in facilitating a wide rangeof solid-liquid separation operations. The polymeric flocculants may beused to dewater suspended solids and other industrial sludges, for thedrainage of cellulosic suspensions such as those found in paperproduction and for the settlement of various inorganic suspensions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the present invention. They are not tobe construed to limit the claims in any manner whatsoever.

EXAMPLES 1 TO 9

A cationic acrylamide polymer is prepared by emulsion polymerization.The aqueous phase is made by dissolving 87.0 gms of commercial, crystalacrylamide monomer, 210.7 gms of 75% acryloxyethyltrimethylammoniumchloride, 4.1 gms of ammonium sulfate, 4.9 gms of 5%ethylenediaminetetraacetic acid (disodium salt), 3.68 gms of 1.5%2-propanol, as chain-transfer agent, 1.0 gm. of 0.245t (10 ppm)methylenebisacrylamide, as branching agent (Example 5B), and 2.56 gmst-butyl hydroperoxide, as a polymerization initiator, into 189.3 gms ofdeionized water. The pH is adjusted to 3.5 (+0.1) by adding sulfuricacid.

The oil phase is prepared by dissolving 12.0 gms of sorbitan monooleateinto 173.4 gms of low odor paraffin oil.

The aqueous phase and oil phase are mixed together and homogenized untilthe particle size is in the 1.0 micron range.

The emulsion is then transferred to a one liter, three-necked, creasedflask equipped with an agitator, nitrogen sparge tube, sodiummetabisulfite activator feed line and thermometer.

The emulsion is then agitated, sparged with nitrogen and the temperatureadjusted to 25° C. (±1° C.). After sparging for 30 minutes, 0.8% sodiummetabisulfite (MBS) solution is added at a rate of 0.028 ml/min. Thepolymerization is allowed to exotherm and the temperature is controlledwith ice water. When cooling is no longer necessary to maintain therequired temperature, the 0.8% MBS solution addition rate is increasedand a heating mantel applied to maintain the temperature. The totalpolymerization time takes approximately 4 to 5 hours. The finishedemulsion product is then cooled to 25° C. The experiment is repeatedvarying the amounts of isopropyl alcohol (IPA) and methylenebisacrylamide (MBA) in proportion to base monomer. The solutionviscosity and the solubility quotient are determined and set forth inthe Table 1, below. Solution viscosity and solubility quotient (CEQ %)are determined by preparing aqueous emulsion solutions. A 0.2% aqueoussolution of the emulsion product is prepared by dispersing 1.70 grams of34% emulsion product into a one liter beaker containing 298 grams ofdeionized water and 0.2 gram of breaker surfactant. The dispersion isagitated at 250 rpm for 2 hours on a magnetic stirrer with a 6 cm longby 1 cm diameter magnetic stirring bar. The solution is then furtherdiluted to 0.1% for solution viscosity and unsheared CEQ determinations.

A 0.1%.sheared solution is also prepared for comparison purposes.Unsheared 0.1% solution, prepared from the 0.2% solution, as definedabove, is transferred into a 30 oz. Waring blender glass jar having aninside diameter of about 7 cm and four rotatable blades that are about 4cm in diameter, 2 blades pointing upward at about 30° angles and twoblades pointing downward at 30° angles. The blades are 1 mm thick andare rotated at about 12,100 rpm for two hours. The solution temperatureis kept at or below 25° C. during this two hour shearing period.

Solution viscosity is determined by adding 5.84 gms of sodium chlorideto 100 grams of 0.1% sheared or unsheared polymer solution and stirringslowly for 15 minutes. The viscosity is then determined by using a ModelLVT Brookfield viscometer with UL adapter at 60 rpm, at 25° C. (±0.1°C.).

Solubility quotient (CEQ %) is determined by measuring solutioncationicity using colloid titration in accordance with theabove-mentioned CEQ technique as described in Vol. 62, No. 7, Journal ofChem. Ed., July 1985, pp. 627-629. The compositions used and the resultsobtained are set forth in Table 1.

                  TABLE 1    ______________________________________    SOLUBILITY AND SOLUTION VISCOSITY    OF CATIONIC ACRYLAMIDE/Q-9 COPOLYMERS    EX-  Q-9    AM-  Mole   IPA    MBA       S.V.  CEQ  CEQ(S)                                                  IR    PLES %      %      wppm  mppm  mPa · s                                         %    %     %    ______________________________________    1A*  40     0      5     3.9   1.81  18.0 76.8  76.6    1B*  40     0      10    7.8   1.71  16.0 66.0  75.8    1C*  40     0      20    15.6  1.55  16.2 69.0  76.5    1D*  40     0      30    23.4  1.39  11.8 42.9  72.5    1E*  40     0      50    39.0  1.41  6.5  25.6  97.0    1F*  40     0      100   78.0  1.26  4.1  12.6  67.5    2A*  40     0.125  20    15.6  1.49  13.7 56.1  75.6    2B*  40     0.25   20    15.6  1.78  29.5 96.9  69.6    3A*  40     0.5    0     0     3.67  85.6 94.3  9.2    3A   40     0.5    5     3.9   3.98  79.9 98.5  18.9    3B   40     0.5    10    7.8   3.53  66.4 97.0  31.5    3C   40     0.5    15    11.7  2.75  54.6 92.2  40.8    3D   40     0.5    25    19.5  1.80  30.6 93.7  67.3    4A*  40     1.0    0     0     2.94  90.0 93.7  3.9    4A   40     1.0    5     3.9   3.19  84.1 92.5  8.4    4B   40     1.0    10    7.8   3.34  87.1 94.0  7.3    4C   40     1.0    15    11.7  2.71  53.7 95.2  4.4    4D   40     1.0    25    19.5  1.92  31.5 94.0  62.5    4B*  40     1.0    50    39.0  1.48  16.3 76.5  78.7    5A*  40     1.5    0     0     2.12  95.8 97.0  1.2    5A   40     1.5    5     3.9   2.76  93.4 94.6  1.3    5B   40     1.5    10    7.8   2.74  91.6 95.2  3.8    5C   40     1.5    20    15.6  3.01  92.8 94.3  1.6    5B*  40     1.5    50    39.0  1.74  27.0 90.4  70.1    5C*  40     1.5    100   78.0  1.46  14.1 72.9  80.7    6A*  40     2.0    0     0     2.24  97.5 98.8  1.3    6A   40     2.0    5     3.9   2.36  97.6 97.6  0    6B   40     2.0    10    7.8   2.45  92.8 94.3  1.6    6C   40     2.0    15    11.7  2.44  96.4 97.3  0.9    6D   40     2.0    25    19.5  2.50  97.6 97.6  0    6E   40     2.0    50    39.0  2.81  92.8 94.3  1.6    7A   40     4.0    25    19.5  1.90  96.9 97.6  0.7    7B   40     4.0    50    39.0  2.18  92.7 94.6  2.0    7C   40     4.0    100   78.0  1.92  54.0 95.5  43.5    8A*  20     0      10    6.2   2.01  21.4 73.8  71.0    8B*  20     0      25    15.5  1.43  10.3 37.3  72.4    8A   20     1.5    10    6.2   2.69  79.8 83.2  4.1    8B   20     1.5    25    15.5  3.20  65.0 80.6  19.4    9A*  60     0      10    9.4   1.69  15.5 79.1  80.4    9B*  60     0      25    23.5  2.46  8.8  62.2  85.9    9A   60     1.5    10    9.4   2.49  83.5 88.3  5.4    9B   60     1.5    25    23.5  2.46  82.7 85.3  3.0    ______________________________________     * = Control Sample     (S) = sheared polymer solution     Q9 = acryloxyethyltrimethylammonium chloride     IPA = isopropyl alcohol, chaintransfer agent     MBA = methylenebisacrylamide, branching agent     S.V. = solution viscosity     IR =  CEQ(S)CEQ!/CEQ(S)     wppm = weight parts per million     mppm = molar parts per million

Table 1 demonstrates the huge, beneficial effect of addingchain-transfer agent on the solubility and solution viscosity propertiesof branched cationic copolymers of acrylamide prepared by incorporatinga difunctional monomer into the polymer chain. The observablecationicity, CEQ, is a direct measure of the solubility of thecopolymer. Soluble copolymers possess a solubility quotient of greaterthan 30 percent, and those below 30 percent are deemed insoluble. Thesolution viscosity is a measure of molecular weight of the copolymer andshows all soluble copolymers to possess very high molecular weights,greater than 1 million.

As can be readily seen from Example 1, the incorporation of evenextremely small amounts, 5 wppm, of branching agent causesinsolubilization of the copolymer in the absence of any chain-transferagent. However, soluble, highly branched products with high molecularweight are readily obtainable by the addition of chain-transfer agent,IPA, in optimum concentrations.

Examples 2A and 2B indicate that polymers falling outside the scope ofthose claimed in the present invention are produced following the artrecognized usage of low quantities of chain-transfer agent.

It can be noted that applying shear to the polymer solution does notsignificantly affect the solubility of polymers with optimumconcentrations of chain-transfer agent, e.g., Samples 4A, 4B, 5A, 5B,5C, 6A, 6B, 6C, 6D, 6E, 7A, 7B, 8A, 9A and 9B. However, the CEQ(S) datain Table 1 do correspond with allegations in the prior art, thatshearing can render insoluble polymers soluble, as discussed above. Notethat, in Table 1, IR=(CEQ(S)-CEQ)/CEQ(S), and is a measure of ionicregain. Polymers exhibiting a high IR value are not necessarilyinsoluble as claimed in the prior art, and thus IR is not a measure ofsolubility. IR is simply a measure of cationicity which is recovered ina shearing process. Polymers produced in accordance with this inventionpossess a wide range of IR values and solubility is not a function ofthe IR value. Polymers such as 6A and 6E have an IR value of 0 and asolubility quotient of 97.6 percent.

EXPERIMENTS 10-11

Branched copolymers are prepared in the same manner as in Example 1except that polyethyleneglycol (MW=600) dimethacrylate (PEGDMA) issubstituted as the branching agent for MBA. Solution viscosity andsolubility of sheared and unsheared copolymers are determined and setforth in Table 2, below.

                  TABLE 2    ______________________________________    SOLUTION VISCOSITY AND SOLUBILITY OF 40:60    Q9-AMD COPOLYMERS PREPARED WITH PEGDMA    IPA        PEGDMA      S.V.    CEQ  CEQ(S)                                              IR    Example           %       wppm    mppm  mPa · s                                       %    %     %    ______________________________________    10     1.5     49.4    7.8   2.93  76.5 89.5  14.5    11     1.5     123.4   19.5  1.88  45.0 90.4  50.2    ______________________________________     AMD = acrylamide     SEE LEGEND OF TABLE 1

As shown in Table 2, above, unsheared, soluble, highly branched, highmolecular weight polymers in accordance with this invention can beprepared with alternative branching agents.

EXAMPLE 12

A cationic acrylamide copolymer is prepared by gel (dry powder)polymerization. 89.98 gms of acrylamide, 218.20 gms of 75%acryloxyethyltrimethylammonium chloride, 0.2 gm of 10%diethylenetriaminepentaacetate (pentasodium salt), 15.0 gms adipic acid,1.1 mls. of 20% sulfuric acid, 2.54 gms 1% sodium hypophosphite (100 ppmon monomer), 1.0 gm of 0.254% methylenebisacrylamide are dissolved in412.33 gms deionized water. The monomer make-up solution is placed in aone quart polymerization vessel equipped with a nitrogen sparge tube,thermometer and activator addition ports. The solution is sparged withnitrogen gas for 30 minutes. During sparging, the solution temperatureis adjusted to 6.0° C. (±1° C.). After sparging, 10 ml of 2%2,2-azobis(2-methyl-2-amidinopropane) dihydrochloride, 0.8 ml of 0.25%ammonium persulfate and 0.8 ml 0.25% ferrous ammonium sulfatehexahydrate polymerization activators are added. As soon as the monomermake-up thickens, the nitrogen sparge tube is raised to the top of thepolymerization vessel. The polymerization exotherms in an insulatedcontainer to maximum temperature, at which time, it is placed in an ovenset at 70° C. for 8 hours. The resulting tough gel is reduced to 1/8inch gel worms, which are air dried for two hours at 65° C. and thenreduced to 9-20 mesh powder. Solubility and solution viscosity aredetermined in the same way as in Example 1 and the results are set forthin Table 3, below.

                  TABLE 3    ______________________________________    SOLUTION VISCOSITY AND SOLUBILITY OF 40:60    Q9:AMD COPOLYMER-GEL POLYMERIZATION    HYP        MBA         S.V.    CEQ  CEQ(S)                                              IR    Example           ppm     wppm    mppm  mPa · s                                       %    %     %    ______________________________________    12A*   0       5       3.9   (i)   --   --    --    12B*   0       25      19.5  (i)   --   --    12C*   75      25      19.5  (i)   --   --    12A    100     5       3.9   2.83  84.6 87.7  1.2    12B    100     10      7.8   2.88  87.0 92.5  1.1    12C    100     25      19.5  2.98  86.8 89.8  1.1    ______________________________________     * = Control Sample     HYP = sodium hypophosphite     mppm = molar parts per million     (i) = insoluble

Table 3 demonstrates that this invention can be used to prepareunsheared, soluble, highly branched, high molecular weight copolymers bygel polymerization and that any chain-transfer agent can be used so longas it is applied in optimum concentration.

EXAMPLES 13-17

Various copolymer products are tested as agents for releasing water fromsewage sludge at several different dosage levels to determine optimumcake solids. Predetermined amounts of a 0.2% aqueous solution of thecopolymers are mixed into 200 gms of sewage sludge in a 400 ml beakerusing a three bladed eturbine stirrer for 3 minutes at 750 rpm. Theflocculated sludge is allowed 3 minutes of free drainage in an 8 cm tubecontaining a piece of filter medium. Then, another piece of filtermedium is placed on top of the sludge cake, and using a piston press,pressure is applied for a total of 6 minutes in accordance with thefollowing schedule; 0.1 min. at 10 psi, 0.1-2 min. at 20 psi, 2-3 min.at 30 psi and 3-6 min. at 40 psi. The sludge cake is removed from thefilter medium, weighed, dried for 16 hours at 95° C., reweighed andpercentage cake solids determined. For comparison purposes, shearedpolymers are also prepared and tested as agents for releasing water fromsewage sludge. The sheared polymers are prepared by shearing a 0.1weight percent solution of various unsheared polymers in a Silverson L2Rmixer. The Silverson mixer is equipped with a square hole, high shearscreen and 3 mm diameter impeller that is rotated at 3000 rpm for 15minutes. A cooling bath is used to keep the shearing solution at about22° C. during the 15 minute shearing period. This degree and method ofshearing represents the typical shearing of the prior art as disclosedin EP 0201237 Column 11, lines 17-19. The results are set forth in Table4, below.

                                      TABLE 4    __________________________________________________________________________    DEWATERING OF GREENWICH, CT 1°/2° SLUDGE            Example            13A               13B                  13C (S)                      14A                         14B                            14C (S)                                15A 15B (S)                                        16 (m)*                                            17 (p)*            Previous Example            5B 1B*                  1B* (S)                      5C 1C*                            1C* (S)                                1F* 1F* (S)                                        --  --    __________________________________________________________________________    Material    AMD, %  60 60 60  60 60 60  60  60  --  --    Q-9, %  40 40 40  40 40 40  40  40  --  --    IPA, %  1.5               0  0   1.5                         0  0   0   0   --  --    MBA,    wppm    10 10 10  20 20 20  100 100 --  --    mppm    7.8               7.8                  7.8 15.6                         15.6                            15.6                                78.0                                    78.0                                        --  --    Properties    S.V., mPa · s             2.74                1.71                  --   3.01                          1.55                            --   1.26                                    --  --  --    S.V. (S), mPa · s            -- --  1.70                      -- --  1.62                                --   1.31                                        --  --    CEQ, %  91.6               18.0                  --  92.8                         16.2                            --  4.1 --  --  --    CEQ (S), %            -- -- 19.6                      -- -- 14.5                                --  39.0                                        --  --    Cake Solids, %    6.7, lb/ton            28.6      27.9              23.2                                            20.0    7.8, lb/ton            30.3      29.2              28.4                                            22.9    9.0, lb/ton            30.6      30.3              28.4                                            31.0    10.1, lb/ton            30.7               A  A   31.1                         A  A           21.1                                            25.2    11.2, lb/ton            29.0               A  A   27.9                         A  A    15.6, lb/ton               A  27.4   A  28.0    17.9, lb/ton               22.8                  29.9   A  29.0    20.1, lb/ton               25.7                  29.7   A  29.4    22.3, lb/ton               28.8                  30.8   21.8                            32.0    24.6, lb/ton         -- 29.6    26.8, lb/ton         28.8                            --    31.3, lb/ton         28.5    35.7, lb/ton         28.3   A   A    120.7, lb/ton               22.1                                    27.1    136.8, lb/ton               27.1                                    29.0    __________________________________________________________________________     (S) = sheared polymer     * = control sample; 16 (m) and 17 (p) represent stateof-the-art commercia     cationic polyacrylamides     AMD = acrylamide     Q9 = acryloxyethyltrimethylammonium chloride     IPA = isopropyl alcohol     MBA = methylene bisacrylamide     S.V. = solution viscosity     lb/ton = pounds of real polymer per ton of dry sludge     A = Did not form a cake.

Table 4 clearly shows that the polymers of this invention consistentlygive higher cake solids than other polymers of the prior art and performat significantly lower dose levels than the sheared, insoluble branchedpolymers. Furthermore, while it was confirmed that although shearingimproved performance of insoluble polymers, it is still substantiallyinferior to the unsheared copolymers of this invention. A furtheradvantage of the copolymers of this invention is that high cake solidsare obtained over a wide dose range.

EXAMPLES 18-21

The procedure of Example 13 is repeated using a different sludgematerial. In Examples 18 and 19 an alternative mixing method is used.Instead of using a three blade turbine stirrer, the polymer and sewagesludge are tumbled in a 1 quart jar for 3 minutes at 45 rpm. The cakesolid percentage is determined and the results are set forth in Table 5,below.

                                      TABLE 5    __________________________________________________________________________    DEWATERING STAMFORD, CT 1°/2° SLUDGE-EFFECT OF MIXING    Previous     IPA                    MBA     Cake Solids, %    Example         Example              Mix                 %  wppm                        mppm                            6.2**                               8.2**                                  12.4**                                      16.4**                                          24.6**                                              32.8**    __________________________________________________________________________    18A  5B   T  1.5                    10   7.8                            23.9                               24.4                                  25.5                                      25.1                                          25.4                                              23.8    18B  1B*  T  0  10   7.8                            A  21.6                                  21.6                                      --  24.7                                              21.6    18C (s)         1B* (S)              T  0  10   7.8                            A  22.0                                  24.1                                      23.6                                          24.1                                              22.8    19A  5C   T  1.5                    20  15.6                            22.9                               24.9                                  --  24.6                                          26.5                                              26.3    19B  1C*  T  0  20  15.6   A  --  20.0                                          24.6                                              22.8    19C (s)         1C* (S)              T  0  20  15.6   A  --  21.9                                          24.4                                              21.6    20A  5B   Tr 1.5                    10   7.8   24.5                                  25.7                                      27.4                                          25.8                                              27.6    20B  1B*  Tr 0  10   7.8   A  24.9                                      24.4                                          25.6                                              19.5    20C (s)         1B* (S)              Tr 0  10   7.8   A  24.3                                      23.6                                          25.3                                              21.9    21A  5C   Tr 1.5                    20  15.6   24.9                                  25.8                                      28.2                                          24.7                                              25.4    21B  1C*  Tr 0  20  15.6   A  21.5                                      23.3                                          25.2                                              24.9    21C (s)         1C* (S)              Tr 0  20  15.6   A  23.4                                      23.7                                          25.1                                              24.0    __________________________________________________________________________     * = Control Sample     ** = Dose in pounds of real polymer per ton of dry sludge     T = Tumble mix method     Tr = Turbine blade mix method     A = Did not form a cake

Again, polymers of this invention outperform insoluble branched polymersand sheared polymers and perform at lower dose levels. The method ofmixing can be seen to have no significant effect on the performance ofthis invention's polymer flocculant product.

EXAMPLES 22 AND 23

The procedure of Example 13 is repeated varying the level of cationicityand using two sludge types. The results are set forth in Table 6, below.

                                      TABLE 6    __________________________________________________________________________    1°/2° SLUDGE DEWATERING - EFFECT OF CATIONICITY    __________________________________________________________________________           Previous                IPA   MBA        Q-9         Cake Solids %    Example           Example                %     wppm                          mppm   Mole %                                     SLUDGE  11.11**                                                 16.67**                                                        22.22**                                                            33.33**    __________________________________________________________________________    22A    8B   1.5   25  15.5   20  St      21.4                                                 21.2   22.3                                                            22.0    22B    8B*  0     25  15.5   20  St      A   --     21.0                                                            21.7    22C    8B* (S)                0     25  15.5   20  St      A   --     22.1                                                            23.3    __________________________________________________________________________    Previous  IPA MBA     Q-9      Cake Solids %    Example         Example              %   wppm                      mppm                          Mole %                              SLUDGE                                   6.3**                                      7.4**                                         8.4**                                            9.5**                                               10.5**                                                   12.0**                                                       21.0**                                                           25.2**                                                               29.4**    __________________________________________________________________________    23A  9A   1.5 10  9.4 60  G    27.2                                      29.8                                         30.0                                            31.0                                               30.8    23B  9A*  0   10  9.4 60  G                    A   28.8                                                           26.8                                                               25.6    23 (S)         9A* (S)              0   10  9.4 60  G                    A   --  27.8                                                               30.0    __________________________________________________________________________     * = Control Sample     ** = Dose in pounds of real polymer per ton of dry sludge     St = Stamford, CT     G = Greenwich, CT     A = Did not form cake.     (S) = Sheared

The unsheared, branched, soluble copolymer of this invention outperformsboth the insoluble and the sheared, branched copolymers producing higherpercentages of cake solids at lower dose levels.

EXAMPLES 24-30

The procedure of Example 13 is repeated, varying the concentration andtype of branching agent. The results are set forth in Table 7, below.

                                      TABLE 7    __________________________________________________________________________    STAMFORD, CT SLUDGE 1°/2° DEWATERING - EFFECT OF BRANCHING    AGENT                 Branching Agent    Previous  IPA                 WT.                    MOLAR      Cake Solids, %    Examples         Example              %  ppm                    ppm   Type 6.4**                                  8.6**                                     10.8**                                         12.9**                                              15.1**                                                  17.2**                                                      21.5**                                                          25.8**                                                              30.2**    __________________________________________________________________________     24*  2A* 0.125                 20 15.6  MBA            24.4 --  --  27.2                                                          28.1                                                              25.0     25*  2B* 0.25                 20 15.6  MBA     25.5                                     --  27.0         27.1    26   5C   1.5                 20 15.6  MBA  27.7                                  29.6                                     29.5                                         28.8 27.5                                                  --    27   4C   1.0                 15 11.7  MBA  26.1                                  28.1                                     29.6                                         31.1 28.0                                                  27.4    28   4B   1.0                 10  7.8  MBA  28.6                                  28.8                                     27.8                                         27.8 27.9                                                  26.5    29   10   1.5                  49.4                     7.8  PEGDMA  28.5                                     30.4                                         27.9 29.8                                                  28.8    30   11   1.5                 123.4                    19.5  PEGDMA  27.0                                     --  29.9 --  29.2                                                      29.2                                                          28.0    __________________________________________________________________________     * = Comparative Example     ** = Dose in pounds of real polymer per ton of dry sludge     MBA = methylenebisacrylamide     PEGDMA = polyethyleneglycol dimethacrylate

Improved dewatering results of this invention are once again easily seenfrom Table 7, above, when an alternative branching agent is used,producing higher cake solids at lower dose levels.

EXAMPLES 31-35

The procedure of Example 13 is repeated using a variety of IPA and MBAconcentrations. The results are set forth below in Table 8, below.

                                      TABLE 8    __________________________________________________________________________    STAMFORD, CT 1°/2° SLUDGE DEWATERING    Previous  IPA                 MBA     Cake Solids, %    Example         Example              %  wppm                     mppm                         12.2*                            15.2*                               18.3*                                  21.3*                                     24.4*                                        27.4*                                           30.5*                                              36.6*                                                 42.7*                                                    48.8*                                                       62.0*    __________________________________________________________________________    31A  3B   0.5                 10   7.8                         A     31.7                                  32.8                                     32.9    31B  3C   0.5                 15  11.7                         A     31.7                                  -- 34.4                                        34.1                                           35.4    31C  3D   0.5                 25  19.5      A  -- 33.9                                        32.2                                           32.1    32A  4A   1.0                  5   3.9                         A  -- 31.2                                  33.0                                     31.0                                        -- 29.6    32B  4B   1.0                 10   7.8                         A  -- 31.6                                  33.2                                     30.4    32C  4C   1.0                 15  11.7         -- A  32.5                                           33.2                                              34.8                                                 34.9                                                    33.3    32D  4D   1.0                 25  19.5            30.8                                        -- 34.9                                              32.6                                                 32.7    33 .sup.         5B   1.5                 10   7.8                         31.9                            31.3                               32.3                                  32.3                                     31.3    34A  6B   2.0                 10   7.8            30.8                                        -- 31.6    34B  6D   2.0                 15  11.7                         29.1                            -- 30.0                                  -- 29.1                                        29.7    34C  6C   2.0                 25  19.5                         28.9                            -- 31.2                                  -- 29.8                                        29.5    34D  6E   2.0                 50  39.0                         A  -- 29.8                                  -- 27.3                                        26.5    __________________________________________________________________________                         17.8*                            22.3*                               26.7*                                  31.2*                                     35.6*                                        44.5*    __________________________________________________________________________    35A  7A   4.0                 25  19.5                         29.0                            30.1                               32.8                                  30.4    35B  7B   4.0                 50  39.0                         30.9                            -- 31.4                                  31.8                                     32.0    35C  7C   4.0                 100 78.0                         A  29.2                               30.8                                  33.8                                     34.5                                        32.7    __________________________________________________________________________     * = Dose in pounds of real polymer per ton of dry sludge     A = Did not form a cake

Table 8, above, further shows that higher cakes solids and superiordewatering are obtained with a range of unsheared, soluble, branchedcopolymers prepared with IPA and MBA.

EXAMPLE 36

The lowest molecular weight copolymer of this invention is analyzed forbulk viscosity at low concentration for comparison with low molecularweight branched copolymers of Pech, Fr 2,589,145. The results are setforth in Table 9, below.

                                      TABLE 9    __________________________________________________________________________    BULK VISCOSITY OF COPOLYMER    EXAMPLE 7C    Previous   Q-9 IPA MBA     Polymer                                    Bulk viscosity.sup.1    Example         Example               Mole %                   %   wppm                           mppm                               Conc. %                                    mPa · s    __________________________________________________________________________    36A  7C    40  4.0 100 78.0                               1.00 1,168    36B  7C    40  4.0 100 78.0                               1.66 2,240    36C  7C    40  4.0 100 78.0                               2.32 5,570    __________________________________________________________________________     .sup.1 Brookfield viscometer (#2 spindle), 30 RPM, 25° C.

The polymers of this invention are of much higher molecular weight thanthose disclosed in Pech. The polymers disclosed in Pech had viscositiesof 2200 to 3600 mPa•s at a concentration of 20 weight percent. Polymersof this invention have a viscosity of 5,570 mPa•s at a significantlylower concentration of only 2.3 weight percent, i.e. they are of muchhigher molecular weights.

EXAMPLE 37

The procedure of Example 1 is repeated to produce sheared and unshearedpolymeric flocculants possessing substantially the same solubility andviscosity characteristics for comparison purposes. The sheared polymersolution, 37B*, is produced by shearing for 60 minutes at 5000 rpm witha Silverson homogenizer. Dewatering is carried out using a tumble mixingmethod of Greenwich, Conn. 1°/2° sludge. Polymer solutioncharacteristics and dewatering application results are set forth inTable 10, below.

                                      TABLE 10    __________________________________________________________________________    PROPERTIES AND SLUDGE DEWATERING CHARACTERISTICS    OF SHEARED AND UNSHEARED 40:60 Q-9:AMD COPOLYMERS    Previous  IPA                 MBA     S.V.                             CEQ                                Dose**                                    Cake Solids                                          Yield                                             Cake    Example         Example              %  wppm                     mppm                         mPa · s                             %  lb/ton                                    %     %  Rating    __________________________________________________________________________    37A* 1B*  0   10  7.8                         1.71                             16.0                                31.9                                    A     A  --                                39.8                                    24.6  93.6                                             2                                47.8                                    23.1  90.6                                             2    37B* 1B* (S)              0   10  7.8                         1.88                             45.8                                27.9                                    25.2  84.9                                             4                                31.9                                    24.5  96.2                                             2                                35.8                                    26.3  88.0                                             4    37A  3D   0.5                  25 19.5                         1.80                             30.6                                27.9                                    24.2  92.2                                             2                                31.9                                    23.8  91.2                                             2                                35.8                                    25.6  98.4                                             1    37B  7C   4.0                 100 78.0                         1.92                             54.0                                27.9                                    24.4  96.2                                             2                                31.9                                    26.4  99.0                                             0                                35.8                                    24.7  95.2                                             3    __________________________________________________________________________     IPA = isopropyl alcohol, chaintransfer agent     MBA = methylenebisacrylamide, branching agent     ** = pounds of real polymer per ton of dry sludge     A = Did not form a cake.     Q9 = acryloxyethyltrimethylammonium chloride     S.V. = solution viscosity     wppm = weight parts per million     * = control sample     mppm = molar parts per million

The yield, in Table 10, is a measure of the yield of dry sludge afterthe belt press procedure has been completed. The cake rating is aqualitative description of the physical properties of the cake where arating of 5 is the worst case, the cake being very sticky and difficultto remove from the filter press medium, thus resulting in a dirtyfilter. A rating of 0 represents the best case, where the cake releasesvery easily from the press material leaving it clean with no residualparticles of sludge.

It can be seen from Table 10 that, while a sheared polymer possessingsubstantially the same viscosity and solubility characteristics as apolymer of this invention produced similar cake solid percentages atequivalent dose levels, the yield of sludge and the cake quality areinferior. High dry sludge yield is desirable for economy, and non-stickyeasily removed cakes are desirable for ease of filter cleaning and thuslong filter life. Both Examples 37A and 37B represent polymerspossessing similar solution viscosity values as the sheared polymer,37B*, with 37A having a slightly lower CEQ% and 37B having a slightlyhigher CEQ%. It can also be seen that shearing does not cause asubstantial increase in polymer viscosity. Example 37B* is sheared at arate of 5000 rpm for about 1 hour; this represents the conventionalmanner of application of the prior art. As previously mentioned, thisexpensive and time consuming practice is unnecessary for the applicationof polymeric flocculants of this invention which are produced inready-to-use form.

EXAMPLES 38-40

Branched homopolymers of acrylamide are prepared in the presence of achain-transfer agent by the emulsion polymerization procedure describedin Example 1. For comparison purposes sheared and unsheared branchedhomopolymers of acrylamide without the addition of a chain-transferagent are also prepared. Shearing is performed for 15 minutes at 3000rpm. The polymers are then tested as flocculants in a silica settlingapplication. The silica settling procedure comprises treating an aqueousmixture of 150 gms of silica (-200 mesh) dispersed in one litre of waterwith 0.027 lbs/ton of polymer. The results and compositional informationare set forth below in Table 11.

                  TABLE 11    ______________________________________    FLOCCULATION OF SILICA WITH HOMOPOLYACRYLAMIDE    IPA        MBA           S.V.     Settling Rate    Example           %       wppm     mppm   mPa · s                                          cm/sec    ______________________________________    38     1.0     7.5      3.5    3.28   0.618    38A*   0       7.5      3.5    1.85   0.452    38A(S)*           0       7.5      3.5    1.66   N.F.    39     1.0     15       7.0    2.88   0.511    39A*   0       15       7.0    1.55   0.382    39A(S)*           0       15       7.0    1.51   N.F.    40     1.0     25       11.5   2.02   0.470    40A*   0       25       11.5   1.29   N.F.    40A(S)*           0       25       11.5   1.28   N.F.    ______________________________________     * = Control Sample     (S) = Sheared Polymer     S.V. = Solution Viscosity     IPA = Isopropyl alcohol     MBA = Methylenebisacrylamide     N.F. = No floc formed.

As can clearly be seen from Table 11, above, the unshearedhomopolyacrylamide of the present invention possesses characteristics asdefined in the appended claims and outperforms homopolyacrylamidesprepared without any chain-transfer agent. Note that shearedhomopolyacrylamides are not useful in silica flocculation applications.

EXAMPLES 41-43

Various branched cationic acrylamide copolymers are prepared in thepresence of chain-transfer agent by the emulsion polymerizationprocedure described in Example 1. For comparison purposes, cationicacrylamide copolymers are also prepared without chain-transfer agent.The results are set forth in Table 12, below.

                  TABLE 12    ______________________________________    PREPARATION OF BRANCHED CATIONIC COPOLYMERS    Cationic    Mole    IPA    MBA        S.V.    Example           Monomer  %       %    wppm   wppm  mPa · s    ______________________________________    41     A        40      1.5  25     25.4  2.10    41*    A        40      0    25     25.4  1.80    42     B        10      1.5  25     14.2  2.24    42*    B        10      0    25     14.2  1.45    43     C        10      1.5  25     13.0  2.17    43*    C        10      0    25     13.0  1.50    ______________________________________     * = Control Sample     A = methacryloxytrimethylammonium methosulfate     B = methacrylamidopropyltrimethylammonium chloride     C = diallyldimethylammonium chloride

As can be seen from Table 12, above, other cationic copolymers havingcharacteristics defined in the appended claims are formed.

EXAMPLE 44

A branched cationic homopolymer of dimethylaminoethylacrylate methylchloride salt is prepared in the presence of chain-transfer agent by theemulsion polymerization procedure described in Example 1. For comparisonpurposes, sheared and unsheared branched homopolymers ofacryloxyethyltrimethylammonium chloride (Q-9) without the addition ofany chain-transfer agent are also prepared. Shearing is performed for 15minutes at 3000 rpm. Sludge dewatering tests, as defined above, areperformed and the results along with compositional data are set forthbelow in Table 13, below.

                  TABLE 13    ______________________________________    DEWATERING OF GREENWICH, CT 1°/2° SEWAGE SLUDGE-    Q9 HOMOPOLYMERS                             S.V.                Cake    Exam- IPA    MBA         mPa ·                                  CEQ  Dose Yield                                                 Solids    ple   %      wppm    mppm  s    %    lb/ton                                              %    %    ______________________________________    44    1.0    35      44.1  2.00 39.1 21.9 84.3 21.8                                         25.5 89.0 23.6                                         29.2 98.0 24.0                                         32.8 93.2 23.2    44*   0      25      31.5  1.84 26.5 21.9 A                                         25.5 A    A                                         29.2 81.0 22.2                                         32.8 89.7 23.5    44(S)*          0      25      31.5  --   --   21.9 85.9 22.6                                         25.5 86.1 22.1                                         29.2 81.6 24.4                                         32.8 95.2 21.9    ______________________________________     * = Control Sample     lb/ton = pounds of real polymer per ton of dry sewage sludge     A = Did not form a cake solid.     (S) = Sheared polymer

Table 13, above, demonstrates that cationic homopolymers of Q-9 possesscharacteristics as defined in the appended claims and exhibit betteroverall flocculating capabilities than sheared and unsheared Q-9homopolymers prepared without the addition of chain-transfer agent.

EXAMPLES 45-47

Again following the procedure of Example 44, homopolymers are preparedfrom 45) methacryloxytrimethylammonium chloride; 46)methacrylamidopropyltrimethylammonium methosulfate and 47)diallyldimethylammonium chloride. Similar, high molecular weight,branched, water-soluble polymers are recovered.

EXAMPLES 48-51

Following the procedure of Example 28, non-ionic, branched,water-soluble, high molecular weight homopolymers are prepared from 48)N-methylacrylamide; 49) N,N-dimethylacrylamide; 50) N-vinylpyrrolidoneand 51) N-vinylmethylacetamide. In each instance, excellent polymersresult.

EXAMPLES 52-55

Again following the procedure of Example 1 except that the acrylamide isreplaced by 52) N-methylacrylamide; 53) N-vinylmethylformamide, similarcopolymers are produced.

The above mentioned patents and publications are incorporated herein byreference.

Many variations of the present invention will suggest themselves tothose skilled in this art in light of the above detailed description.For example, instead of using methylenebisacrylamide as a branchingagent, any polyfunctional monomer compound may be used, includingglycidyl acrylate; dialdehydes, such as glyoxal, and the like. A numberof chain-transfer agents may be used instead of isopropyl alcohol, suchas sodium hypophosphite; mercaptans; sulfites, and the like.

Monomers may include any ethylenically unsaturated acrylic or vinylmonomers. Other useful monomers may comprise sodium acrylate;2-acrylamidomethylpropane sulfonate; vinyl acetate, and the like. Alsocontemplated are all methods of polymerization and dewatering processes.

All such obvious modifications are within the full intended scope of theappended claims.

EXAMPLE 56 Preparation of a High Molecular Weight, Branched, SolubleDimethylaminomethylpolyacrylamide and its Quaternized Derivative

To 378 parts of the backbone polyacrylamide from Example 39 is added amixture of low odor paraffin solvent (106 parts) and sorbitan monooleate(9 parts). A preformed mixture of 60% aqueous dimethylamine (39) partsand 37% aqueous formaldehyde is then added with mixing over 1/2 hourkeeping the temperature below 30° C. The reaction is then completed byheating for 204 hours at 40° C. Then, 5.2% quanidine nitrate (30) parts)is added to give the dimethylaminomethylated polyacrylamide with 22.7%polymer solids and a CEQ of over 30%.

In a pressurized reactor, methyl chloride (54 parts) is added over 2hours to 238 parts of the dimethylaminomethylated polyacrylamideprepared above. This mixture is then heated to 38° C. for 3 hours toensure complete quaternization. The resultant quaternizeddimethylaminomethylated polyacrylamide has a CEQ of over 30%.

Both high molecular weight, highly branched, soluble, quaternized andunquaternized dimethylaminomethylated polyacrylamides are effectiveflocculants and dewatering aids.

We claim:
 1. A method of releasing water from a dispersion of suspendedsolids which comprises (a) adding to the dispersion, as a true solution,from about 0.1 to about 50,000 parts per million of dispersion solids ofan unsheared, branched, water-soluble, cationic, polymeric flocculant,said polymeric flocculant having a solution viscosity of at least about1.8 mPa•s measured in a Brookfield viscometer with a UL adapter at 25°C. on a 0.1 percent, by weight, polymer solution in 1M NaCl at 60 rpm, asolubility quotient of greater than about 30 percent, and a branchingagent content of from about 4 to about 80 molar parts per million basedon initial monomer content, and (b) dewatering the mixture of thedispersion of suspended solids and the polymeric flocculant.
 2. A methodas defined in claim 1 wherein the polymeric flocculant has a solubilityquotient of greater than about 40 percent.
 3. A method as defined inclaim 1 wherein the polymeric flocculant has a branching agent contentof from about 8 to about 20 molar parts per million based on originalmonomer content.
 4. A method as defined in claim 1 wherein the polymericflocculant has a solution viscosity of at least about 2.0 mPa•s measuredin a Brookfield viscometer with a UL adapter at 25° C. on a 0.1 percent,by weight, polymer solution in 1M NaCl at 60 rpm.
 5. A method as definedin claim 4 wherein said solution viscosity is at least about 2.2 mPa•s.6. A method as defined in claim 5 wherein said solution viscosity is atleast about 2.4 mPa•s.
 7. A method as defined in claim 1 wherein saidpolymeric flocculant is a polymer formed from one or more ethylenicallyunsaturated monomers selected from acrylamide; methacrylamides;N-alkylacrylamides, N,N-dialkylacrylamides; N-vinyl methylacetamide;N-vinyl methyl formamide; vinyl acetate; N-vinyl pyrrolidone;N,N-dialkylaminoalkylacrylates or methacrylates and their quaternary oracid salts; N,N-dialkylaminoalkyl-acrylamides and methacrylamides andtheir quaternary or acid salts or diallyl dimethylammonium acid salts.8. A method as defined in claim 7 wherein said polymeric flocculant is apolymer formed from one or more ethylenically unsaturated monomersselected from acrylamide; N,N-dialkylaminoalkylacrylates andmethacrylates and their quaternary or acid salts, or diallyldimethylammonium acid salts.
 9. A method as defined in claim 8 whereinsaid polymeric flocculant is a polymer formed from acrylamide incombination with at least one cationic monomer.
 10. A method as definedin claim 9 wherein said polymeric flocculant is a polymer formed fromacrylamide and acryloxyethyltrimethylammonium chloride.